1. Field of the Invention
The present invention relates to laminated filters and particularly relates to a laminated LC filter including a resonant circuit including an inductor and a capacitor.
2. Description of the Related Art
As a known technique, Japanese Unexamined Patent Application Publication No. 2005-229434 discloses a laminated filter 101 configured as shown in FIGS. 8 and 9, for example. FIG. 8 is an exploded perspective view illustrating the laminated filter 101, and FIG. 9 is a perspective view illustrating the appearance of the laminated filter 101. As shown in FIG. 8, the laminated filter 101 is configured such that a coil section 110 including coil patterns 111a to 116a and a capacitor section 130 including capacitor patterns 131a to 133a are laminated with each other in this order from the top.
The coil section 110 is configured such that insulation layers 111 to 116 including the coil patterns 111a to 116a formed thereon, respectively, are laminated on one another. The coil patterns 111a to 116a are electrically connected to one another in a helical manner at end portions thereof using penetration electrodes 111b to 115b disposed in the insulation layers 111 to 115, respectively.
The coil pattern 111a extends to an end portion of one of the shorter sides of the insulation layer 111 and is electrically connected to an external electrode 102 of the laminated filter 101. The coil pattern 116a extends to an end portion of one of the shorter sides of the insulation layer 116 which is an opposite side relative to the one of the shorter sides of the insulation layer 111 and is electrically connected to another external electrode 104 of the laminated filter 101.
The capacitor section 130 is configured such that insulation layers 131 to 133 having capacitor patterns thereon are laminated on one another. Capacitor patterns 131a and 133a are formed substantially in centers of the insulation layers 131 and 133, respectively, and have a substantially rectangular shape. The capacitor patterns 131a and 133a include a pair of extension patterns 131b and a pair of extension patterns 133b, respectively, which are exposed to end surfaces of respective longer sides of the laminated filter 101. The capacitor patterns 131a and 133a are electrically connected to an external ground electrode 106 through the extension patterns 131b and 133b. 
The capacitor pattern 132a is formed in a substantially center of the insulation layer 132 and has a substantially rectangular shape. The capacitor pattern 132a includes an extension pattern 132b which is exposed to an end of one of the shorter sides of the laminated filter 101 and is electrically connected to the external electrode 102 through the extension pattern 132b. 
The capacitor pattern 132a is disposed between the capacitor patterns 131a and 133a, and two capacitors are formed, that is, a capacitor including the capacitor patterns 132a and 131a with the insulation layer 131 interposed therebetween and a capacitor including the capacitor patterns 132a and 133a with the insulation layer 132 interposed therebetween.
In recent years, as high-frequency electronic apparatuses including cellular phones are miniaturized, miniaturization and reduction of height of electronic components have been demanded. In the known laminated filter 101, since only a coil pattern or only a capacitor pattern is formed on a single insulation layer, a certain number of insulation layers should be laminated on one another so that desired characteristics are obtained. Therefore, there arises a problem in that the number of insulation layers included in the laminated filter 101 increases and accordingly the height is not reduced.
Furthermore, in the known laminated filter 101, as shown in FIG. 8, the coil patterns 111a to 116a and the capacitor patterns 131a and 133a are laminated on one another in a lamination direction, and therefore, when current is supplied to the coil patterns 111a to 116a, a magnetic flux is generated through the capacitor patterns 131a to 133a. Accordingly, there arises a problem in that eddy current is generated in the capacitor patterns 131a to 133a and a Q characteristic of the laminated filter 101 is deteriorated due to eddy current loss.
Furthermore, in the known laminated filter 101, there arises another problem in that the Q characteristic of the laminated filter 101 is deteriorated due to undesired inductance components generated in an external electrode section since the coil section 110 and the capacitor section 130 are electrically connected to each other through the external electrodes 102 and 104.